Modern surgery often requires the injection of large amounts of fluid into various parts of the body. Particularly, where reconstructive surgery is concerned, relatively large amounts of local anesthetics are injected into the subcutaneous tissues during surgery. These fluids often comprise local anesthetics which must infiltrate the entire area which is to be reconstructed.
Conventional hypodermic syringes having only a fluid containing cylinder and a fluid displacing piston are unsuitable for use in such surgery. Rather, syringes capable of pumping relative large amounts of such anesthetic on a substantially continuous basis must be used. Typically, such syringes employ biasing springs to return the fluid displacing piston to its original position after being depressed into the fluid displacing position. A check valve connecting the fluid cavity of the syringe with a fluid supply is included so that the physician can continually pump the handles of such a device to deliver a large quantity of fluid into the body.
Presently available syringes or pumps of the type described are bulky and virtually impossible to use in modern reconstructive surgery. Typically, these devices have springs which are external to the syringe cylinder to bias the piston to an extended position. Pump handles extend from the cylinder in a fashion similar to a conventional grease gun to depress the bias spring and fluid displacing piston. Thus, a serious disadvantage of the described device is that operation of the device in close proximity to the body is impaired by the projecting spring and handles. The construction of the device is necessarily complex and, therefore, costly. Devices of the type described are typically not disposable due to their expense. Therefore, a need exists for a disposable infiltration pump which provides minimum obstruction to close maneuvers about the body for the injection of subcutaneous tissue with suitable medications.
The described devices are also limited in that the biasing mechanisms cannot be adapted to conventional syringes for more conventional uses. For example, when a standard syringe is to be filled with a fluid prior to an injection, the user must puncture a vial constaining medication with the hypodermic needle and then draw the piston to fill the cylinder with medicine while holding the vial relative to the cylinder. Typically, the piston is then slightly depressed to bring fluid in the cylinder to the correct volume and to expel air. This procedure is wasteful, time consuming and inconvenient. It would be desirable to utilize the piston biasing technique of the previously described pump devices to draw fluid from the medicine vial in a controlled manner. However, the high cost, bulk and structural limitations of the described device precludes its use in this situation.